Re: [boost] advice needed for Boost.svg_plot

From: Giovanni Piero Deretta (gpderetta_at_[hidden])
Date: 2007-07-04 10:51:21

On 7/4/07, Jake Voytko <jakevoytko_at_[hidden]> wrote:
> On 7/4/07, Phil Endecott <spam_from_boost_dev_at_[hidden]> wrote:
> >
> > Jake Voytko wrote:
> > >   plot_range(my_plot, data.begin(), data.end(),
> > >                   default_functor, human_age,
> > >                   circle,
> > >                   orange, red,
> > >                   3, 10);
> >
> > It would be great to be able to write just 'data' in place of
> > 'data.begin(), data.end()'.  Is there anything stopping this?
>
> The STL algorithm functions are used as the basis here, and it carries all
> of the same benefits. First, you can select a small subset of your data if
> you'd like that to be plotted (for example, plotting a single year out of
> 100 years of data).

You can do the same with a range based interface, you just need to
pass to boost::make_iterator_range() the iterators defining your
subrange.
Most of the time you might want to plot a whole container, so the range based
algorithm is easier to use. Not considering that you can chain the
result of lazy
algorithms:

  plot_range(my_plot, filtered(data, point_selector));

It is hard to do the same with an iterator interface. In general range
based interfaces are superior to iterator based ones. Range based
algorithms might
even appear in the next C++ standard.

>Second, the interface itself almost completely weeds out
> noncompliant functions, as functions without iterator support won't compile,
> and the error message will (usually) show on the line in the user's code
> where the error is.

SFINAE using an hypothetical is_range trait [1] can help here.

HTH,

gpd

[1] some one is was working on a container traits library a while ago,
and I believe a subset of it is already present in the detail of some
boost library.